1. Field of the Invention
The present invention relates to a laser processing apparatus that performs laser processing on a workpiece such as a semiconductor wafer or the like held on a chuck table.
2. Description of the Related Art
In a semiconductor device manufacturing process, a plurality of regions are partitioned by division lines arranged in a lattice manner on the front surface of a semiconductor wafer in substantially the shape of a disk, and devices such as ICs, LSIs, or the like are formed in the partitioned regions. The regions in which the devices are formed are then divided from each other by cutting the semiconductor wafer along the division lines. The individual semiconductor devices are thus manufactured.
Recently, in order to improve the throughput of a semiconductor chip such as an IC, an LSI, or the like, a semiconductor wafer has been put to practical use in which semiconductor devices are formed by a functional layer including a low dielectric constant insulator film (low-k film) laminated on the front surface of a substrate such as silicon or the like, the low dielectric constant insulator film being formed by a film of an inorganic material such as SiOF, BSG (SiOB), or the like, or a film of an organic material which film is a polyimide-based polymer film, a parylene-based polymer film, or the like.
Division along the division lines of such a semiconductor wafer is generally performed by a cutting device referred to as a dicing saw. This cutting device includes a chuck table holding the semiconductor wafer as a workpiece, cutting means for cutting the semiconductor wafer held on the chuck table, and moving means for moving the chuck table and the cutting means relative to each other. The cutting means includes a rotary spindle rotated at a high speed and a cutting blade mounted on the spindle. The cutting blade includes a disk-shaped base and an annular cutting edge mounted on the side surface of an outer circumferential portion of the base. The cutting edge is for example formed by fixing diamond abrasive grains having a grain size of approximately 3 μm by electroforming.
However, the above-described low-k film is difficult to cut by the cutting blade. That is, the low-k film is very fragile like mica. Therefore, when the semiconductor wafer is cut along the division lines by the cutting blade, the low-k film peels off, and this peeling reaches circuits and causes a fatal damage to the devices.
In order to solve this problem, Japanese Patent Laid-Open No. 2005-64231 discloses a wafer dividing method including irradiating both sides in a width direction of a division line formed on a semiconductor wafer with a laser beam along the division line, thereby forming two laser-processed grooves and dividing a laminate including a low-k film along the division line, and positioning a cutting blade between the outsides of the two laser processed grooves and moving the cutting blade and the semiconductor wafer relative to each other, thereby cutting the semiconductor wafer along the division line.